This invention relates to digital conferencing techniques which are applicable both to voice and data or combinations of each.
In time division communication systems one conference technique is to sum all of the speaker samples belonging to the conference. This conference sum is then delivered to each conference station, minus the sample from that station. A second conference technique is to have a processor combine only those samples going to a particular station. Thus, a given conference will have as many subcombinations as there are stations. The first approach has the advantage of requiring relatively few logic steps for each conference but has the disadvantage that fully flexible gain adjustment is not possible except for very small conferences. The second approach, while allowing individual station gain adjustment, suffers from its dependence upon a large number of logic operations for a given conference.
An example of the first approach is seen in U.S. Pat. No. 4,229,814 while an example of the second technique is seen in U.S. Pat. No. 4,059,735.
Thus, in a system where large numbers of stations may be connected together in conference fashion, or where large numbers of small conferences are necessary, it is important to be able to manage the system within the time constraints imposed by the time division network. It follows then that one could reduce the number of time slots in order to manage more processing per each frame, or one could increase the speed of the processor to perform more steps within the time allowed. Each of these solutions, however, have practical limits and are only marginally effective.
Accordingly, it is desired to design a digital time division communication system having large conference capability without affecting the number of time slots and without requiring super fast processors.